Gyroscopic devices commonly rely upon rotating elements to provide reference orientations relative to one or more axes in coordinate space. Certain known gyroscopic devices also rely upon vibrating beams or wires to identify reference planes in which the beams or wires vibrate in order to provide output responses representative of movements relative to the reference planes. Devices of these types are described in the literature. (E.g., U.S. Pat. Nos. 3,504,554; 3,903,747; 3,538,774; and 3,992,952).
The vibrating wire gyroscope may be broken into two distinct classes, namely vibrating wire rate gyroscopes and vibrating wire position gyroscopes. A vibrating wire position gyroscope is described in U.S. Pat. No. 3,106,847 ('847). Vibrating position gyroscopes may be driven along the axis of the wire, as in '847. Alternatively, vibrating position gyroscopes may be driven in a direction perpendicular to the wire, but continuously aligned to the vibration plane of the wire. Continuous alignment of the vibration drive force can be accomplished by four electrostatic plates as described, for example, in U.S. Pat. No. 3,538,774.
Vibrating wire rate gyroscopes may be driven perpendicular to the wire in a direction which remains constant relative to the associated housing. This type of drive is the simplest to implement, and therefore the least costly to manufacture. An example of this type of instrument is disclosed in U.S. Pat. No. 3,515,003. The driving force is accomplished by passing alternating current through the wire, which is in a permanent magnet field.
Sensing the motion of the wire presents technological challenges. Prior designs utilizing capacitance measurements and electromagnetic measurements encountered difficulties in avoiding undesirable interaction between the drivers and sensors. Some designs use two antinodes with one node in the center with the wire vibrating at its second harmonic so that one side of the wire may be excited and the other side sensed. Other designs use high frequency modulation and demodulation to separate the sensors from the drivers.
In conventional vibrational gyroscopic devices, the bandwidth of the motion signal from a lateral drive vibrating element is limited to the bandwidth of the vibrating element. Therefore, there is a need for a device that obtains a high bandwidth motion signal from a lateral drive vibrating instrument with a low bandwidth (high Q, low natural frequency vibration) vibrating element.
Such gyroscopic devices, when incorporated into input pointer devices for controlling the position of display cursors in television or computer systems, thus alleviate the need for physical reference surfaces against which operator's manual movements in relation to such reference surfaces can be sensed and translated into coordinate information for positioning displayable cursors.
Such gyroscopic devices can thus replace conventional mouse-type input devices that require a physical support surface with respect to which relative movement can be sensed for positional information that is then used to manipulate a cursor in a computer-controlled display system.